Opacifier for enamels



Patented Dec. 2, 1930 UNITED STATES PATENT oFFIca 1 THOw H. MOKEOWN, OF METUOHEZN, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- IENTS, TO THE IROlESSLER & HASSLAGEER CHEMICAL COMPANY, A CORPORATION OF DELAWARE OTPACIFIEIB. FOR ENAMELS Ho Drawing.

This invention relates to the manufacture of white vitreous enamels and has for its object the development of an enamel utilizin a relatively inexpensive opaclfier wh ch impart to the enamel adesirable whlte color. A further object is to provide such an enamel particularly suited for wet process application on cast metal, such as cast iron or steel. p

.My invention consists-in providing enamel mixtures containing sodium antimonate and tin oxide as opacifier. I have tried various mixtures of sodium antimonataand tin oxide in a number "of varied formulae, but I have found that the best results vare secured if the two constituents are present in a more or; less restricted ratio to each other. I have found that the sodium antimonate-tin oxide ratios should be approximately 3: 1. If this ratio is alteredin either direction the enamel in which it is used does not have the desired opacity and physical .properties. vI have ,4 found that in the enamels of myinvention. this 3: 1 mixture can be utilized in amounts sufiicient to give desired opacity and color,

. and. still not render the enamel brittle or increase its tendency to chip ofi, i. e. the proper cubical expansion. of the enamel necessary to secure theproper adherence to the 1; have further discovered that to secure the? proper adherence and other desirable qualities in such enamels several components must be used in more or less definite proportions- The following example gives these .components in the preferred proportions and:

the variable allowances which maybe made in the components to secufesmall variations in'theexpansion coefiicient to conform to the Application filed January 12, 1925. Serial 110. 246,399.

can bemade up to fit any particular cast metal.

In this example and in the appended claims my opacifier is referred to as antimony-tin opacifier, and the amount "required denotes the amount of 3:1 mixture use Wet process cast iron enamel Variable gg? frlt allow" formula F'eldspar (parts by weight) 12. 5 10 to 14 Flint (parts by weight) 8. 7 7 to 10 Borax (parts by weight)..." 23. 4 21 to 24 Boric acid (parts by weight} 3. 4 3 to. 5 Soda nitre (parts by weight 2. 6 1 to 3 Cryolite (parts by weight)" 5. 2 4 to 8 Fluorspar (parts byweigbt) 3.4 3 to 6 Barium carbonate (parts by weight). 12. 15 11 to 18 Red lead (parts by weight) 11. 1 10 to 17 Whiting (parts by weight 5.2 3 to 7 Zmc oxide (parts by welg 1a)-- 6. 0 4 to 7 Antimony-tin opacifler (parts by welght) 6. 0 1 to 12 1 Mill batch Variable batch allowances formula Frit (parts by weigh 100 Antimony-tin opacifler (parts by weight)-.. 2 1 to Clay (parts by weight) 6 4 to MgSOl plus 7151 0 (parts by Weight) 5 4 to Water (parts by weight) 35 25 to i The powdered materials of the frit for Bleak-f mula are mixed by hand or mechanically,

and then fused; the melt -is dropped'into" water to cool and shatter after which it is weighed and placed in the ball mill together with the remaining constituents ofi the mill batch. These materials are then ground to a fineness best; suited for the par ticular method of application to be used; this fineness will be 3070 mesh. In using this enamel on cast iron, for example, a special ground coat isnot' required,

generally between about but instead a thin coat of the enamel composition is first applied. The primary coat is first applied to the steel and burned on, or fired, at a temperature somewhat higher than that required to mature the enamel. This temperature will be above about 650 C. After burning the primary coat and cooling the article, the regular enamel slurry or paste is applied by any suitable means, such as dipping or spraying; the article is then dried and burned at a temperature of about 650 C. A period of about 5 minutes at the maturing temperature is usually satisfactory. When thus burned the above enamel has the following empirical formula calculated on a basis wherein the sum of the sodium, potassium, calcium, barium, lead and zinc oxides is equal to one.

Mols Ea) 0.314 2 0.022 CaO 0.236 BaO 0.146 PbO 0.112 ZnO 0.170 ea 3a 2 s Sb O 0.032 SiO 0.760 S110 0.024 F2 The coetficient of expansion obtained with the preferred formula is 316.3 X 10".

The variable compositions allowable in this flux will result in fluxes having a variable pomposition by weight approximately as folows:

NilgO 6 t0 K Q 0.8 to 1.2 CaO 4 to 8.3 A1 0 4.3 to 7 13 0 9.3 to 11.6 Sb O 0.6 to 8 SiO 15 to 22 SnO l to 12 F 2 to 4.3 BaO S to 10 PbO -1 10 to 17 ZnO 4 to 7 In the above formulae it will be noted that the opacifier allowances cover a wide range; the actual amount to be used depends on the opacity desired. In the above example part of the opacifier has been added in the enamel formula and part in the mill batch. This, however, is an optional procedure and depends upon the color desired in the enamel. The opacifier can all be added to the raw frit formula before smelting, or it can all be added to the mill batch, or it can be distributed between the two batches in the amounts indicated above or in any other desired distribution. If all of the opacifier added to the mill batch the resulting enamel will have a slight creamy tint, whereas if all of the opacifier is added to the raw frit batch before smelting a bluish white enamel results; if the opacifier is distributed between the two batches the tint will vary between the two extremes in about the ratio of the additions.

IVhile I have explained the opacifier as being a definite mixture of the two materials, I have found that it is not necessary to actually mix or grind the antimonate and tin oxide together before adding them to the enamel. I have found that the opacifying results are equally well secured if, for example, the two were mixed prior to the addition of the enamel, or whether they were added separately, the only requirement being that the ratio approximately be maintained. Furthermore, I have found that all of the antimonate can be added to the raw frit formula and the tin oxide added to the mill batch. Regardless of how the two materials are added any deviation from the ratio 3:1is immediately apparent by a change in the appearance and properties of the enamel. It can be seen from the above I do not Wish to be limited to the manner of adding my opacifying mixtures to the enamel. The sodium antimonate of my antimony-tin opacifier may be supplied by pure sodium antimonate as such, or I may use the material commonly known in the art as leukonin which consists chiefly of sodium antimonate, and therefore in the appended claims, I wish it understood that sodium antimonate is intended to cover such mixtures, and the term antimony tin opacifier is intended to cover such materials as leukonin in combination with tin oxide as well as the pure material.

Formulae suited for sheet steel and dry process cast iron enameling embodying my invention are given in my copending applications, Serial No. 246,397 and Serial No. 246,398 respectively, filed of even date herewith.

Claims:

1. An enamel composition comprising the following materials withinthe range of pro- Parts by weight F eldspar 12.5 Flint 8.7 Borax 23.4 Boric acid v 3.4 Soda nitre 2.6 Cryolite' 5.2 Fluorsparu I a 3.4: Barium carbonateu' 12.5 Red lead 11.1 Whiting 5.2 Zinc .oxide 6.0 Antimony-tin opacifier (3: 1) 6.0

2. An enamel composition comprising:

3. A fired enamel having a composition by Weight approximately Within the range of proportions as follows: I

Na O "6 to 11 K 0 0.8 to 1.2 CaO 4 to 8.3 A1 0 4.3 to 7 B 0 9.3 to 11.6 Sb O 06 to 8 S10 15 to 22 S1102 1 t0 F 2 to 4.3 Ba() 8 to 10 PbO 10 to 17 ZnO 4 to 7 wherein sodium antimonate and tin oxide are utilized in the requisite amount in the preparation of the composition for firing and in the ratio to-each other of 3 to 1.

4. A fired enamel having the following empirical formula:

Hols. Na o 0.314 K 0 0.022 CaO 0.236 BaO 0.146 PbO 0.112 3% L 352 B2 0; 0134s gb os 0.0732 i 0. S116 0.024. F 2- 0.146

Signed at Perth Amboy, in the county of Middlesex and State of New Jersey this tenth (lay of January, A. 'D. 1928.

y f H. M KEOWN 

